small part in cast iron

Discussion in 'Lost PLA casting' started by dtsh, Feb 5, 2019.

  1. dtsh

    dtsh Silver

    I've been a mostly silent reader here for a couple years and I'm slowly (oh so slowly) working on a small aluminum furnace, but this particular project is beyond my capabilities so I'm looking for a little help casting it.

    My mother has an old rocking recliner from the 1800's which she's had since I was a boy, but one of the pivots broke about 30 years ago so it has been purely decorative since that time. My mother is and has been active in making and fixing things most of her life, though admittedly she's slowed down a lot in the last few years. Anyways, a few months back we had been talking on the phone about casting things while I was in the early stages of planning my aluminum furnace and she asked if I could make a new part for the chair. She sent me the original, unbroken part from the other side as a reference; so when I modeled it I went ahead and modeled both sides as one part. I could make something in steel, or with some effort, aluminum or bronze, but since the original is cast iron I thought that would be the best choice for a replacement.

    I modeled the original in CAD and have made a 3d print to serve as a pattern and included what is hopefully enough draft to make it a usable pattern. It will be sanded and painted to provide as smooth of a finished pattern as I can make it. I'm looking at this as a good hands-on opportunity to try out new skills while waiting on my own furnace to be ready.

    Pictures speak 1000 words, so here are two views of the original, unbroken part with a US quarter for scale.

    chair_part1.jpg

    chair_part2.jpg

    This is an earlier printed pattern, the current one includes more draft on the inside of the tubes and a slight teaking of mounting hole placement, but is otherwise the same. This is prior to sanding, priming, and painting of course. The original part shows cut marks in what would be the middle of the two parts, so I modeled it with about 1/2" of extra material between the parts in case a riser or gate needs to be added there.
    chair_part3.jpg

    I'm no rich man, but I do understand the value of a man's time and skill. Any input and assistance is greatly appreciated.
     
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    Your probably going to want to fill in those holes and drill them out later to avoid having to core them. Im about a week away from being set back up and running. If no one else offers then just send me the cad file (and one with the holes removed) and ill pour one for you..... Ill try to get it with the holes cast in in first. Did you allow for shrink on the pattern?
     
  3. dtsh

    dtsh Silver

    I had considered that, but it looks to me like the draft on the original allowed it to be cast face down. I certainly can remove them if that makes it easier, I was just following what looked to be the original design. The mounting holes look like they may have been drilled though.

    Preferred format(s) for the CAD file? I'm using FreeCAD and it appears to support a variety of export options.

    I've read about it so should know better, but I did not. I will edit accordingly tonight.

    Thanks for the offer, it is much appreciated. I'll update after I've had a little time to make the appropriate edits.
     
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    After thinking about it for a minute send me the file as a finished part (no draft) I've been wanting to try some lost pla ceramic shell iron casting... stl format is fine...
     
  5. Zapins

    Zapins Gold

    That's a cool project. Nice of you to do it David :)

    I want to see how iron works with ceramic shell. I suspect it will do very well but I haven't personally done it yet. Be sure to post those juicy pics when its done.
     
    DavidF likes this.
  6. dtsh

    dtsh Silver

    Attached are two STL files, with and without mount holes. If there are any other alterations please let me know and I'll do my best to make them happen.
    Once again, thanks very much for the assistance.
     

    Attached Files:

    DavidF likes this.
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    I'll probably video it...:cool:
    Hoping it goes smoothly in lost pla, if not there's all ways sand casting o_O

    Dtsh, did you scale it for shrink??
     
  8. dtsh

    dtsh Silver

    From what I've read, the shrink on cast iron is around 1%. When I modeled it I added a fair bit more than 1% due to being worried that such thin section wouldn't cast, so assuming expected shrink is less than 5% I think it can be safely ignored.

    Please correct me if my assumptions are incorrect.
     
  9. DavidF

    DavidF Administrator Staff Member Banner Member

    If its not a high tolerance part then it probably does not.... Just wanted to check before I started printing it...
     
  10. DavidF

    DavidF Administrator Staff Member Banner Member

    Printing complete....
    Now to model and print the sprue and gating system.....
    20190206_130634.jpg
     
    Mark's castings, dtsh, Mach and 2 others like this.
  11. oldironfarmer

    oldironfarmer Silver

    Is that for green sand?:rolleyes:
     
  12. Mister ED

    Mister ED Silver

    Subscribing for updates. :)
     
  13. Jason

    Jason Gold

    wouldn't it be faster and easier to just tig some steel tube on a plate? shape and drill???
     
  14. dtsh

    dtsh Silver

    It would and if it were just a chair that's what I would do, except mig as that's what I have available, but this is a chair from the mid 1800's or so and she'd prefer to keep it close to what it was originally even if it's not all original.
     
    Mister ED likes this.
  15. oldironfarmer

    oldironfarmer Silver

    I was hoping you would get a sand casting, for that reason. Still interesting to see the lost PLA.
     
  16. dtsh

    dtsh Silver

    Me too, but I'll take what I can get and I too am interested to see what the lost PLA looks like.
     
  17. DavidF

    DavidF Administrator Staff Member Banner Member

    I'll shot peen it when done to give it more of a sand cast look If need be...
     
    oldironfarmer likes this.
  18. _Jason

    _Jason Silver

    I'd be curious to see your shot peen set up. That's something I've sort of looked for online but haven't found anything especially useful on for the home gamer.
     
  19. DavidF

    DavidF Administrator Staff Member Banner Member

    It's just a scat-blast, loaded with SS shot...
     
    _Jason likes this.
  20. Jason

    Jason Gold

    Still speaking code David... Jason it's a sandblast cabinet loaded with tiny tiny bb's.
     

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